MEMS-scanning mirror based laser projection systems are promising candidates for use in ultra-small size and portable applications. In an example MEMS-scanning mirror projection system, a mirror may be arranged to be rotated about two mutually orthogonal axes in order to display pixels of a projected image on a projection surface. In particular, the example MEMS-scanning mirror can reflect light emanating from one or more light sources to project the image. In some MEMS-scanning mirror projection systems, two mirrors may be used, each of which may be arranged to be rotated about one of two mutually orthogonal axes. Laser light sources may be modulated while the MEMS mirror is rotated to effectively pulse and display pixels one after another to generate a projected image. In particular, the MEMS mirror can rotate to scan reflected light over an entirety of the area of the projected image at a high enough speed to achieve an image that appears stable to the human eye. Advantageously, according to such a technique, pixels may only be projected when needed, and thus for parts of the projected image that are black, the laser light source(s) may be turned off, conserving power.
One factor upon which the displayed image quality of a MEMS-based projection system may depend is the precision with which the modulated laser pulses are synchronized with the rotation of the mirror. If synchronization between the modulated laser pulses and the rotation of the mirror is poor, then from one frame to the next, the same pixel may be pulsed according to a slightly different timing, creating blur in the image. In order to precisely synchronize the modulated laser pulses with the rotation of the mirror, it may be necessary to be able to precisely sense the rotational angular position of the mirror. A second factor that may influence the image quality is the extent to which the MEMS mirror remains optically flat during operation. During operation, a MEMS mirror may be subject to forces that may cause it to bend, a phenomenon sometimes called dynamic deformation. Bending or other distortion of the mirror may cause corresponding distortion of the image pixels being generated, which may also constitute a source of perceived blur in the image.